Glory
What's that, you say? The old guy who stopped breathing at the movies last week is now up and around at home with his family? His wife, children, and grandchildren are really happy and it's all because of you?
There are few, if any feelings in life than can compare with bringing someone back from death. As an EMT, you get to do just that. Publicly, you'll likely say, "Aw shucks, I was just doing my job." However, to yourself, you'll say, "Wow, that save was a big deal."
Doctors and nurses also save lives, but they do it in a controlled environment like a hospital with all sorts of help and resources available. You do it out in the world where anything can happen and you and your partner are pretty much on your own.
Glory comes not only from saving lives, but by simply helping people who are sick or injured. In fact, non-life threatening incidents will constitute the vast majority of your work. A transport to a doctor's appointment or a scratched knee at a football game will still offer you a great deal of satisfaction. The care you give as an EMT will mean a lot to people, even if they don't say it.
Tangible rewards may also come your way. Examples are award certificates, ceremonies, publicity, discounts, freebies, etc. Good work can also result in pay raises and promotions. You probably won't become an EMT just for these benefits, but they can't hurt.